Radiation Energy Flux Research Articles

The evolution of curvature in planar, photoionization-driven heat fronts

Photoionized plasmas are common in astrophysics and cosmology, especially in space near compact objects, and there are effects from photoionization in high-energy-density plasmas due to the large radiation fields present. Photoionized plasmas are an active area of laboratory research and there are currently experiments to study photoionization-supported heat fronts. These photoionization fronts differ from the physics of diffusive radiation waves, commonly called Marshak waves, that are also an active area of research. This work uses a geometric argument to describe the expected evolution of the photoionization front curvature, in a planar geometry. It then compares this curvature to that of a Marshak wave as a method of diagnosing a heat front experiment. It is found that while the curvature of a planar Marshak wave increases in time, it decreases for a photoionization front. A comparison of radiation energy and electron heat fluxes through the container for the heat front propagating medium demonstrates that the geometric argument for the photoionization front curvature is sufficient. This comparison also demonstrates that wall losses are not significant in a photoionization front because the post-front region is very optically thin. A discussion of the implication this work has on material choice in the targets for an experiment follows.

SEASONAL AND DIURNAL VARIATION OF SURFACE ENERGY FLUXES AND SURFACE CHARACTERISTICS OVER A SEMIARID GRASSLAND IN WEST AFRICA

Radiative fluxes and surface energy fluxes computed using the eddy covariance method from January to December 2013 were used to investigate the partition of energy and energy exchange over degraded grassland in the Sudanian savannah region of West Africa. In Sumbrungu Agunsi, (10.841°N, 0.918°W), in Ghana’s upper east area, an Eddy Covariance station was erected near to the Ghana–Burkina-Faso border. The fluctuations in radiation components, energy fluxes, and surface characteristics components were studied on a seasonal and daily basis. The Incoming shortwave radiation, out-going shortwave radiation, incoming long wave radiation and out-going long wave radiation all varied annually, resulting in a seasonal variation in net radiation. The soil moisture content, evaporative fraction, and the surface albedo were found to be low during the dry season but high during the wet season, while, the Bowen ratio was found to be high during the dry season but low during the wet season. During the wet season, majority of the available energy were converted to latent heat, but, during the dry season, majority of the available energy was transformed to sensible heat. The station’s energy balance closure was investigated; slope of the regression found was 0.67 with an intercept of 33 Wm-2 . The reasons for the station’s energy balance not being closed were investigated.

Тепловое нагружение конструкции отработанной ступени ракеты при баллистическом спуске

The results of a numerical calculation of the aerodynamic heating of a spent rocket stage structural elements during its controlled descent along a ballistic trajectory are presented. The influence of the initial trajectory parameters on the specific convective and radiant heat fluxes is determined. To assess the thermal loading of the spent rocket stage structure, the parameter of the total specific energy flux is introduced. It has been established that in the range of initial speeds of the spent rocket stage from 1800 m/s to 2600 m/s, an increase in the initial speed by 200 m/s leads to an increase in the specific convective flow by an average of 11 % for the tail compartment and the fuel tank and by 5 % for the oxidizer tank. The share of the specific radiant energy flux withdrawn from the surface in relation to the specific convective energy flux is from 0,15 to 0,19 for the tail compartment, from 0,12 to 0,15 for the fuel tank and not more than 0,009 for the oxidizer tank. Empirical dependencies are proposed for the preliminary stage of assessing the temperature state of the spent rocket stage structure when moving on a ballistic trajectory. The error of the calculation results according to the proposed dependencies does not exceed 12 %.

Получение хлопьев высокого пищевого достоинства из зерна ржи

The relevance of the production of grain products of a high degree of readiness and the expansion of the raw material base through the use of rye grain is shown. Methods for determining the fractional composition of proteins according to A.I. Ermakov, the content of water-soluble protein according to O.H. Lowry, dextrins according to M.P. Popov and E.F. Shanenko, fiber according to Kurshner and Ganak were used. Rational modes of IR processing of rye grain are substantiated when obtaining a new product from it in the form of flakes with high nutritional and consumer advantages. The effect of IR treatment on the physical and biochemical properties of rye grain has been studied. It is shown that the main parameters determining the modes of IR processing of rye grain are the grain moisture, the density (intensity) of the incident radiant energy flux and the irradiation time. The influence of various modes of IR processing on carbohydrates and proteins of rye grain has been studied. The effect of the intensity of IR processing of rye grain on the degree of starch dextrinization and on the density of grains is shown. The effect of IR treatment on the change in the solubility of proteins as a result of their denaturation is investigated. The effect of IR treatment modes on the degree of denaturation and fractional composition of rye grain proteins has been studied. The effect of grain flattening on the carbohydrate complex and the intensification of IR processing on the consumer advantages of flakes has been studied. The effect of IR treatment on the acidity of water and alcohol extracts, fiber content has been studied. Physicochemical changes in rye grain during its flattening into flakes after IR treatment have been studied. The production of a new fast food product in the form of flakes with high nutritional value and high fiber content, which can be used as a dry breakfast, is justified.

Numerical study of radiating xenon plasma

In this paper numerical simulation of the spectral properties of xenon plasma is carried out for various parameters (temperature, density, pressure) within the framework of the Saha-Boltzmann approximation. For calculations, pre-prepared atomic databases with varying degrees of detail of ion states were used. The effect of ionization potential depression was taken into account. The spectral absorption coefficients and emissivity, as well as the spectral radiation energy flux for a homogeneous plasma in a spherically symmetric geometry, were obtained. The identification of strong spectral lines in the wavelength ranges of interest has been carried out.

The Contribution of Drifting Snow to Cloud Properties and the Atmospheric Radiative Budget Over Antarctica

AbstractThe Antarctic Ice Sheet experiences perpetual katabatic winds, transporting snow, and moisture from the interior towards the periphery. However, the impacts of Antarctic moisture and drifting snow on cloud structure and surface energy fluxes have not been widely investigated. Here, we use a regional climate model with a newly developed drifting snow scheme to show that accounting for drifting snow notably alters the spatial distribution, vertical structure and radiative effect of clouds over Antarctica. Overall, we find that accounting for drifting snow leads to a greater cloud cover providing an increase of +2.74 Wm−2 in the surface radiative energy budget. Additionally, a comparison with 20 weather stations reveals a 2.17 Wm−2 improvement in representing the radiative energy fluxes. Our results highlight the need to study the impact of drifting snow processes on the future evolution of clouds, the surface energy budget and the vertical atmospheric structure over Antarctica.

Prandtl number dependence of stellar convection: Flow statistics and convective energy transport

Context. The ratio of kinematic viscosity to thermal diffusivity, the Prandtl number, is much smaller than unity in stellar convection zones. Aims. The main goal of this work is to study the statistics of convective flows and energy transport as functions of the Prandtl number. Methods. Three-dimensional numerical simulations of compressible non-rotating hydrodynamic convection in Cartesian geometry are used. The convection zone (CZ) is embedded between two stably stratified layers. The dominant contribution to the diffusion of entropy fluctuations comes in most cases from a subgrid-scale diffusivity whereas the mean radiative energy flux is mediated by a diffusive flux employing Kramers opacity law. Here, we study the statistics and transport properties of up- and downflows separately. Results. The volume-averaged rms velocity increases with decreasing Prandtl number. At the same time, the filling factor of downflows decreases and leads to, on average, stronger downflows at lower Prandtl numbers. This results in a strong dependence of convective overshooting on the Prandtl number. Velocity power spectra do not show marked changes as a function of Prandtl number except near the base of the convective layer where the dominance of vertical flows is more pronounced. At the highest Reynolds numbers, the velocity power spectra are more compatible with the Bolgiano-Obukhov k−11/5 than the Kolmogorov-Obukhov k−5/3 scaling. The horizontally averaged convected energy flux (F̅conv), which is the sum of the enthalpy (F̅enth) and kinetic energy fluxes (F̅kin), is independent of the Prandtl number within the CZ. However, the absolute values of F̅enth and F̅kin increase monotonically with decreasing Prandtl number. Furthermore, F̅enth and F̅kin have opposite signs for downflows and their sum F̅↓conv diminishes with Prandtl number. Thus, the upflows (downflows) are the dominant contribution to the convected flux at low (high) Prandtl numbers. These results are similar to those from Rayleigh-Benárd convection in the low Prandtl number regime where convection is vigorously turbulent but inefficient at transporting energy. Conclusions. The current results indicate a strong dependence of convective overshooting and energy flux on the Prandtl number. Numerical simulations of astrophysical convection often use a Prandtl number of unity because it is numerically convenient. The current results suggest that this can lead to misleading results and that the astrophysically relevant low Prandtl number regime is qualitatively different from the parameter regimes explored in typical contemporary simulations.

Soft gravitational radiation from multi-body collisions

We derive a universal expression for the gravitational radiation energy spectrum dEGW/dω at sub-leading order emitted from a generic gravitational hard scattering of multi-particles or multi-bodies. Our result includes all mathcal{O} (ω) corrections to the gravitational radiation flux from a generic 2 → N collision, in both the cases of massless and massive particles/bodies. We also show the dependence of the radiation energy flux by the quantum spin in case of particle collisions. Then, we consider the specific case of a gravitational elastic scattering of two massive bodies, i.e. m + M → m + M with m, M the masses of the two bodies respectively. We demonstrate that in this case all mathcal{O} (ω) contributions to the energy flux exactly cancel each others. Nevertheless, we also show that, for a 2 → 2 inelastic scattering, the inclusion of sub-leading soft gravitons leads to a not zero radiation flux, having a simple expression in certain asymptotic regimes. Our results can be applied to the case of Black Hole collisions with possible testable implications in gravitational waves physics.

Radiative Energy Flux Variation from 2001–2020

Radiative energy flux data, downloaded from CERES, are evaluated with respect to their variations from 2001 to 2020. We found the declining outgoing shortwave radiation to be the most important contributor for a positive TOA (top of the atmosphere) net flux of 0.8 W/m2 in this time frame. We compare clear sky with cloudy areas and find that changes in the cloud structure should be the root cause for the shortwave trend. The radiative flux data are compared with ocean heat content data and analyzed in the context of a longer-term climate system enthalpy estimation going back to the year 1750. We also report differences in the trends for the Northern and Southern hemisphere. The radiative data indicate more variability in the North and higher stability in the South. The drop of cloudiness around the millennium by about 1.5% has certainly fostered the positive net radiative flux. The declining TOA SW (out) is the major heating cause (+1.42 W/m2 from 2001 to 2020). It is almost compensated by the growing chilling TOA LW (out) (−1.1 W/m2). This leads together with a reduced incoming solar of −0.17 W/m2 to a small growth of imbalance of 0.15 W/m2. We further present surface flux data which support the strong influence of the cloud cover on the radiative budget.

Atmospheric Rivers: An Overlooked Threat to the Marginal Snowpack of the Australian Alps

AbstractAtmospheric rivers (ARs) are tropospheric corridors that provide ~90% of poleward water vapor transport. They are predicted to increase in frequency and intensity if global warming continues unabated. Here we present a case study of the first direct observations of the impact of AR rain-on-snow (RoS) events on the marginal snowpack of the Australian Alps. Reanalysis data show ARs embedded within strong northwesterly airflow extended over 4000 km from the eastern Indian Ocean to southeast Australia, where orographic processes enhanced RoS. We quantify for the first-time radiation and turbulent energy flux exchanges using eddy covariance and the contribution of rain heat flux to the snowpack during the AR RoS events. The hydrological response of an above snow line catchment that includes Australia’s highest peak during the events was rapid, with discharge increasing by nearly two orders of magnitude above historical mean winter discharge. This reflects the isothermal properties of the marginal Australian snowpack, where small increases in energy from RoS can trigger rapid snowmelt leading to flash flooding. Discharge decreased quickly following the passage of the ARs and onset of cold air advection. Based on climate projections of ≈+2.5°C warming in the Australian Alps by midcentury combined with an already historically, close-to-ripe snowpack, we postulate that AR induced RoS events will accelerate the loss of snow cover.

Stray radiation energy fluxes in ITER based on a multiresonator model

Here we re-evaluate the stray radiation loads due to electron cyclotron resonance heating and diagnostic gyrotrons in ITER, as well as compute the stray radiation energy flux due to electron cyclotron emission. Microwave loads due to stray radiation were assessed in the past. We give here more comprehensive estimates, including spatial variations in the machine. We show that for the start-up phase in the First Plasma campaign the threshold of 100 kW/m2, which diagnostics have to be able to withstand, is not exceeded. For the later campaigns, the stray radiation energy flux during start-up and burnthrough will exceed 450 kW/m2. Stray radiation from electron cyclotron emission and from a diagnostic 60 GHz gyrotron can contribute to more than 140 kW/m2 combined.

Dynamics of chemically reactive Jeffery fluid embedded in permeable media along with influence of magnetic field on associated boundary layers under multiple slip conditions

The prime goal of the current pagination is to scrutinize behavior of mixed convective Jeffrey nanoliquid (JNL) flowing over an exponentially stretching sheet by using possessions of radiative energy flux, non-uniformly heated source/sink, slip boundary condition, and modified Arrhenius energy function. The governing physical expression (PDEs) are converted in view of similar ODE’s. Solution of constructed problem is heeded by employing shooting technique. Graphical and tabular results are designed for assisting flow, opposing flow and forced convection cases to scrutinize the performance of miscellaneous significant variables. The results attained exhibited worthy agreement with the preceding remarkable works. The noteworthy finding is Opposing flow case demonstrations higher temperature and concentration profile compared to assisting flow and forced convection case.

Validation of Landsat-8 satellite-derived radiative energy fluxes using wireless sensor network data over Beas River basin, India

ABSTRACT In the present paper, spatio-temporal variability in surface radiative energy fluxes has been estimated for snow/ice-covered Beas River basin, lower Western Himalaya, India using remote sensing technology and evaluated with wireless sensor network (WSN) collected data at various elevation levels. Surface energy fluxes are derived using Landsat-8 satellite images and digital elevation model (DEM) at fine spatial resolution (~30-m) during clear-sky days of the year 2016–2017. RMSE have been estimated in incoming shortwave, incoming longwave, outgoing longwave, net shortwave and net radiation flux and observed to be ~5%, ~ 6.3%, ~2.4%, ~18.9%, and ~28.3% of the respective mean values. Landsat-8 images in conjunction with DEM have shown the potential to retrieve variability in surface radiative energy fluxes at fine resolution in mountain terrain. Additionally, temporal variability in radiative radiation fluxes have also been explored on different elevation ranges and aspects slopes. The high energy fluxes have been estimated on southern slopes during analysis as compared to northern slopes in the present study. The paper appears to be the first for reporting net radiation flux for Himalayan snow cover at 30-m spatial resolution. The satellite-derived energy fluxes may be valuable in various applications associated with climatology, hydrology, wet-snow avalanche detection, land use land cover, mass balance, ecology, etc., especially in the absence of in situ data.

Terrestrial sources of summer arctic moisture and the implication for arctic temperature patterns

Sea ice melt and ocean heat accumulation in the Arctic are strongly influenced by the presence of atmospheric water vapor during summer. While the relationships between water vapor concentration, radiation, and surface energy fluxes in the Arctic are well understood, the sources of summer Arctic water vapor are not, inhibiting understanding and prediction of Arctic climate. Here we use the Community Earth System Model version 1.3 with online numerical water tracers to determine the geographic sources of summer Arctic water vapor. We find that on average the land surface contributes 56% of total summer Arctic vapor with 47% of that vapor coming from central and eastern Eurasia. Given the proximity to Siberia, near-surface temperatures in the Arctic between 90°E-150°E, including the Laptev Sea, are strongly influenced by concentrations of land surface-based vapor. Years with anomalously large concentrations of land surface-based vapor in the Arctic, and especially in the Laptev Sea region, often exhibit anomalous near-surface poleward flow from the high latitudes of Siberia, with links to internal variability such as the Arctic Dipole anomaly.

A Machine Learning Technique for Spatial Interpolation of Solar Radiation Observations

AbstractThis study applies statistical methods to interpolate missing values in a data set of radiative energy fluxes at the surface of Earth. We apply Random Forest (RF) and seven other conventional spatial interpolation models to a global Surface Solar Radiation (SSR) data set. We apply three categories of predictors: climatic, spatial, and time series variables. Although the first category is the most common in research, our study shows that it is actually the last two categories that are best suited to predict the response. In fact, the best spatial variable is almost 40 times more important than the best climatic variable in predicting SSR. Furthermore, the 10‐fold cross validation shows that the RF has a Mean Absolute Error (MAE) of 10.2 Wm−2 and a standard deviation of 1.5 Wm−2. On the other hand, the average MAE of the conventional interpolation methods is 21.3 Wm−2, which is more than twice as large as the RF method, in addition to an average standard deviation of 6.4 Wm−2, which is more than four times larger than the RF standard deviation. This highlights the benefits of using machine learning in environmental research.

Circular Orbit Structure and Thin Accretion Disks around Kerr Black Holes with Scalar Hair

Abstract In this paper, we first investigate the equatorial circular orbit structure of Kerr black holes with scalar hair (KBHsSH) and highlight their most prominent features, which are quite distinct from the exterior region of ordinary bald Kerr black holes, i.e., peculiarities that arise from the combined bound system of a hole with an off-center, self-gravitating distribution of scalar matter. Some of these traits are incompatible with the thin-disk approach; thus, we identify and map out various regions in parameter space. All of the solutions for which the stable circular orbital velocity (and angular momentum) curve is continuous are used for building thin and optically thick disks around them, from which we extract the radiant energy fluxes, luminosities, and efficiencies. We compare the results in batches with the same spin parameter j but different normalized charges, and the profiles are richly diverse. Because of the existence of a conserved scalar charge, Q, these solutions are nonunique in the (M, J) parameter space. Furthermore, Q cannot be extracted asymptotically from the metric functions. Nevertheless, by constraining the parameters through different observations, the luminosity profile could in turn be used to constrain the Noether charge and characterize the spacetime, should KBHsSH exist.

Coherently enhanced microwave pulses from midinfrared-driven laser plasmas.

Ultrafast ionization of a gas medium driven by ultrashort midinfrared laser pulses provides a source of bright ultrabroadband radiation whose spectrum spans across the entire microwave band, reaching for the sub-gigahertz range. We combine multiple, mutually complementary detection techniques to provide an accurate polarization-resolved characterization of this broadband output as a function of the gas pressure. At low gas pressures, the lowest-frequency part of this output is found to exhibit a drastic enhancement as this field builds up its coherence, developing a well-resolved emission cone, dominated by a radial radiation energy flux. This behavior of the intensity, coherence, and polarization of the microwave output is shown to be consistent with Cherenkov-type radiation by ponderomotively driven plasma currents.

Development of a special purpose LED ultraviolet lamp in a T8 flask

Fluorescent tubular ultraviolet lamps are used in medicine, industry, cosmetology, forensic science, and banking. During the development of the LED ultraviolet lamp in a T8 flask, a comparison of its lighting characteristics (power, energy flux, spectral distribution of radiation) with the parameters of special-purpose fluorescent lamps produced at industrial enterprises has been carried out. The design of the LED lamp includes a glass uviole tube with a diameter of 26 mm and a length of 322 mm (wall thickness is 1 mm, glass grade - SL97-3). For precise installation of the lamp in the irradiation facility and supplying electric power to it, plastic caps of the G13 pin type (the distance between the electrical contacts is 12.7 mm) are used. Measurements of electrical parameters, energy flux and spectral distribution of radiation have been carried out at nominal mains voltage on a Gooch &Housegophotocolorimetric measuring device. The developed LED lamp consumes seven times less electricity, has significantly longer (five times) expected service life and is a safer source of ultraviolet radiation, since it does not contain harmful vapors of mercury and its compounds. The LED ultraviolet lamp in a T8 flask can be used instead of the manufactured LUFT-10 lamps for special purposes, namely, in irradiators for carrying out technological processes (photochemical reactions, drying, curing), for attracting and disinsecting insects in traps, in photocopiers.

Spectral energy characteristics of radiation in oxy-coal combustion for energy utilization

In this paper, the radiative energy characteristics, especially the spectral distribution characteristics, of the oxy-fuel combustion of pulverized coal are studied from the perspective of radiative energy utilization. Based on a modified tube furnace test platform, the radiative energy flux and spectral distribution of oxy-fuel combustion for three typical Chinese coals under O2/N2 and O2/CO2 atmospheres in the temperature range of 600–1000 °C are measured online using radiative heat flux sensors. In particular, the radiative exergy and its spectral distribution characteristics are analyzed based on the second law of thermodynamics. It is found that the intensity of the radiative energy and exergy increase, as does the proportion of spectral radiation below the wavelength of 4.1 μm, with the increase of the oxygen ratio and combustion temperature under the experimental conditions. In contrast, different atmospheres are found to have little effect on the radiation characteristics. One-dimensional calculation cases of media radiation transfer constructed according to the combustion characteristics can better reveal the proportional characteristics of the spectral radiation. The results provide a reference for research on the cascade conversion and management of photo-thermal energy in fuel combustion.

Experimental study of the temperature distribution over the surface of a heat supply object under heating conditions with a gas infrared emitter

The experimental studies of the heat transfer processes in the system of radiator – air – heat supply object have been carried out to measure the surface temperatures of the fabric covering the model of the worker. The results obtained give grounds to conclude that when developing systems for ensuring the scheduled thermal regime of the local working zones of the large industrial premises under the conditions of radiant heating, it is necessary to take into account the spatial orientation of the surface areas of the clothing of the worker relative to the vector of the radiant energy flux.